No. 18No. 18

The Lymphatic SystemThe Lymphatic System

Chapter 2 The Chapter 2 The Lymphatic SystemLymphatic System

Section 1 IntroductionSection 1 Introduction

The The lymphatic systemlymphatic system is a separate is a separate vascular system serving as accessory vascular system serving as accessory system for the return of fluid from the system for the return of fluid from the tissue spaces.tissue spaces.

The fluid in the lymphatic vessels is The fluid in the lymphatic vessels is termed lymph. Its composition is similar to termed lymph. Its composition is similar to that of plasma, except for the lower that of plasma, except for the lower concentration of proteins.concentration of proteins.

This system does not open into the heart This system does not open into the heart but into the venous system in the root of but into the venous system in the root of the neck. the neck.

1. Constitution of the lymphatic 1. Constitution of the lymphatic systemsystem

The lymphatic system consists of the The lymphatic system consists of the lymphatic vesselslymphatic vessels, , lymphatic lymphatic tissuetissue, and , and lymphatic organslymphatic organs..

2. functions of the lymphatic system2. functions of the lymphatic system The lymphatic system has several The lymphatic system has several

important functions.important functions. The functions of the lymphatic system The functions of the lymphatic system

include the producing lymph cells, the include the producing lymph cells, the destruction of bacteria, the removal of destruction of bacteria, the removal of foreign particles from the lymph, specific foreign particles from the lymph, specific immune responses, and the return of immune responses, and the return of interstitial fluid to the bloodstream.interstitial fluid to the bloodstream.

Ⅰ Ⅰ The Lymphatic VesselsThe Lymphatic Vessels

The are classified according to size The are classified according to size and structure as and structure as lymphatic lymphatic capillariescapillaries, , lymphatic vesselslymphatic vessels, , lymphatic trunkslymphatic trunks and and lymphatic lymphatic ductsducts..

ⅠⅠ) ) Lymphatic capillaryLymphatic capillary

The lymphatic capillariesThe lymphatic capillaries form network in the form network in the tissue spaces, the meshes of which are larger ttissue spaces, the meshes of which are larger than those of the neighbouring blood capillariehan those of the neighbouring blood capillaries. They often commence with a dilated, bulb-lis. They often commence with a dilated, bulb-like, blind end and their calibre is greater than tke, blind end and their calibre is greater than that of blood capillaries.hat of blood capillaries.

The wall is composed of a single layer of overlThe wall is composed of a single layer of overlapping endothelial cells attached by anchorinapping endothelial cells attached by anchoring filaments to the surrounding connective tissg filaments to the surrounding connective tissue.ue.

Another important feature of the Another important feature of the endothelial wall of the lymphatic endothelial wall of the lymphatic capillaries is that it is permeable to capillaries is that it is permeable to substances of much greater substances of much greater molecular size than those which can molecular size than those which can pass through the endothelial wall of pass through the endothelial wall of blood capillaries.blood capillaries.

Lymphatic capillaries are present in manLymphatic capillaries are present in many tissue of the body, but are absent from y tissue of the body, but are absent from avascular structures (epidermis, hair, naavascular structures (epidermis, hair, nails, cornea, and articular and some other ils, cornea, and articular and some other cartilages), the brain and spinal cord, thcartilages), the brain and spinal cord, the splenic pulp and bone marrow.e splenic pulp and bone marrow.

ⅡⅡ) The ) The lymphatic vesselslymphatic vessels ( (lymphlymphaticsatics))

The lymphatic vessels are united with lymphatic The lymphatic vessels are united with lymphatic capillaries. They have three-layered wall similar capillaries. They have three-layered wall similar to the wall of veins. Their valves, which are more to the wall of veins. Their valves, which are more numerous than in veins, permit lymph to flow in numerous than in veins, permit lymph to flow in only one direction and give lymphatic vessels a only one direction and give lymphatic vessels a characteristic beaded appearance. The lymphatic characteristic beaded appearance. The lymphatic vessels course in close relationship with the veins vessels course in close relationship with the veins of any body part. They exceed the veins in of any body part. They exceed the veins in number, but they are smaller in size and thinner number, but they are smaller in size and thinner walled. At intervals along the course of the walled. At intervals along the course of the lymphatic vessels, lymph nodes are interposed.lymphatic vessels, lymph nodes are interposed.

Likes veins, the lymphatic vessels are arrangeLikes veins, the lymphatic vessels are arranged in superficial and deep sets.d in superficial and deep sets.

The The superficial lymphaticssuperficial lymphatics lie immediately u lie immediately under the skin and may run independently or mnder the skin and may run independently or may accompany the superficial veins; they drain ay accompany the superficial veins; they drain lymph from the superficial structures. The lymph from the superficial structures. The deedeep p lymphaticslymphatics always accompany vascular or n always accompany vascular or neurovascular bundles; they drain lymph from eurovascular bundles; they drain lymph from muscles and internal organs.muscles and internal organs.

ⅢⅢ) The ) The lymphatic trunkslymphatic trunks Having traversed the corresponding nodes, thHaving traversed the corresponding nodes, th

e lymphatic vessels from the various parts of te lymphatic vessels from the various parts of the body unite one another and finally form ninhe body unite one another and finally form nine lymphatic trunks, which are named, e lymphatic trunks, which are named,

The The right and left jugular trunks(2)right and left jugular trunks(2), , the the right and left subclavian trunks(2)right and left subclavian trunks(2), , the the right and left bronchomediastinal trunksright and left bronchomediastinal trunks

(2)(2), , the the right and left lumbar trunks(2)right and left lumbar trunks(2), , and and the intestinal trunk(1)the intestinal trunk(1)..

ⅣⅣ) ) The lymphatic ductsThe lymphatic ducts There are two lymphatic ducts in number.There are two lymphatic ducts in number. The The right lymphatic ductright lymphatic duct is formed by the uni is formed by the uni

on of the right jugular, right subclavian and rigon of the right jugular, right subclavian and right bronchomediastinal trunks. It opens into thht bronchomediastinal trunks. It opens into the right venous anglee right venous angle

The The thoracic ductthoracic duct is formed by the union of th is formed by the union of the right lumbar, left lumbar and intestinal trunke right lumbar, left lumbar and intestinal trunks, at the root of the neck it receives the left jugs, at the root of the neck it receives the left jugular, left subclavian and left bronchomediastiular, left subclavian and left bronchomediastinal trunks. It opens into the left venous angle.nal trunks. It opens into the left venous angle.

ⅡⅡ. The . The lymphatic Tissuelymphatic Tissue

The lymphatic tissue is situated in The lymphatic tissue is situated in the wall of the alimentary, the wall of the alimentary, respiratory, urinary and reproductive respiratory, urinary and reproductive canals. There are two kinds of canals. There are two kinds of lymphatic tissue, that is lymphatic tissue, that is lymph lymph nodulesnodules and and scattered lymphatic scattered lymphatic tissuetissue..

ⅢⅢ. The Lymphatic Organs. The Lymphatic Organs They are lymph nodes, tonsils, spleen and thyThey are lymph nodes, tonsils, spleen and thy

mus.mus. The The lymph nodeslymph nodes:: They are small, round or bean-shaped organs tThey are small, round or bean-shaped organs t

hat are distributed along the course of many ohat are distributed along the course of many of the lymphatic vessels. There are groups of lyf the lymphatic vessels. There are groups of lymph nodes in the groin, axilla, and neck, as wemph nodes in the groin, axilla, and neck, as well as in numerous other deeper locations.ll as in numerous other deeper locations.

They may also be divided into the superficial aThey may also be divided into the superficial and deep groups.nd deep groups.

Each node consists of lymphatic tissue enclosEach node consists of lymphatic tissue enclosed in a fibrous connective capsule.ed in a fibrous connective capsule.

Generally each presents on one side a slight deGenerally each presents on one side a slight depression, termed the pression, termed the hilumhilum, through which th, through which the blood vessels enter and leave the node. The e blood vessels enter and leave the node. The efferent lymph vesselsefferent lymph vessels (usually single) also e (usually single) also emerges from the node at this hilum, while the merges from the node at this hilum, while the afferent vesselsafferent vessels enter it at several different pa enter it at several different parts of the periphery. Lymph passes through sevrts of the periphery. Lymph passes through several groups of lymph nodes before entering theral groups of lymph nodes before entering the blood stream.e blood stream.

Local corresponding lymph nodes:Local corresponding lymph nodes: Lymph from an area of the body is drained intLymph from an area of the body is drained int

o the o the local (regional) corresponding lymph nlocal (regional) corresponding lymph nodesodes..

The lymph nodes can filter out certain amount The lymph nodes can filter out certain amount of microorgainsms and inflammatory productof microorgainsms and inflammatory products. This process often produces tenderness and s. This process often produces tenderness and swelling in nodes of an infect ed area. If bacterswelling in nodes of an infect ed area. If bacteria in an area drained by a node become too nuia in an area drained by a node become too numerous, they may attack the node itself, resultmerous, they may attack the node itself, resulting in an abscess.ing in an abscess.

Lymph node enlargement may be Lymph node enlargement may be local or widespread. Cause of lymph local or widespread. Cause of lymph node enlargement includes infection, node enlargement includes infection, allergy, primary disease of the node allergy, primary disease of the node (such as Hodgkin’s disease, a cancer (such as Hodgkin’s disease, a cancer of the lymph node) and leukemia.of the lymph node) and leukemia.

One feature of the lymphatic system is its One feature of the lymphatic system is its significance in the spread of tumors. significance in the spread of tumors. Cancer usually produces a secondary Cancer usually produces a secondary growth in regional lymph nodes. Many of growth in regional lymph nodes. Many of these secondary growths (metastases) these secondary growths (metastases) result from tumor emboli detaching from result from tumor emboli detaching from the point of origin and lodging in the the point of origin and lodging in the regional lymph nodes. Operations for the regional lymph nodes. Operations for the removal of cancer are therefore planned to removal of cancer are therefore planned to take away the mass of the cancer, the take away the mass of the cancer, the intervening lymphatic vessels and the intervening lymphatic vessels and the lymph nodes.lymph nodes.

Section 2 The Lymphatic DuctsSection 2 The Lymphatic Ducts

ⅠⅠ. The . The Thoracic DuctThoracic Duct (left lymphatic (left lymphatic duct)duct)

It is the largest lymph vessel of the It is the largest lymph vessel of the body and conveys the greater part of body and conveys the greater part of the lymph back into the circulating the lymph back into the circulating blood. In the adult it varies in length blood. In the adult it varies in length from 30-40 cm.from 30-40 cm.

The duct begins at the upper end of the cisterna chyli The duct begins at the upper end of the cisterna chyli near the lower border of the near the lower border of the twelfth thoracic vertebratwelfth thoracic vertebra and enters the thorax through the aortic hiatus of the and enters the thorax through the aortic hiatus of the diaphragm. It ascends through the posterior mediastidiaphragm. It ascends through the posterior mediastinum with the aorta on its left, the azygos vein on its rinum with the aorta on its left, the azygos vein on its right side, the vertebral column on its back, and the esoght side, the vertebral column on its back, and the esophagus on its front. Opposite the phagus on its front. Opposite the fifth thoracic vertebrfifth thoracic vertebraa the thoracic duct passes obliquely behind the esoph the thoracic duct passes obliquely behind the esophagus to its left side, and continues superiorly to the thagus to its left side, and continues superiorly to the thoracic inlet. Then, it arches laterally behind the left caoracic inlet. Then, it arches laterally behind the left carotid sheath at the root of the neck and ends by openirotid sheath at the root of the neck and ends by opening into the left venous angle.ng into the left venous angle.

In the neck it is joined usually by the left jugular trunk, In the neck it is joined usually by the left jugular trunk, the left subclavian trunk and the left bronchomediastithe left subclavian trunk and the left bronchomediastinal trunk.nal trunk.

The The cisterna chylicisterna chyli is an elongated saccular dilatation is an elongated saccular dilatation in the lymphatic route from the abdomen and lower liin the lymphatic route from the abdomen and lower limbs. It is situated in front of the first and second lumbmbs. It is situated in front of the first and second lumbar vertebral bodies, immediately to the right of the abar vertebral bodies, immediately to the right of the abdominal aorta. It receives the right and left lumbar andominal aorta. It receives the right and left lumbar and intestinal trunks.d intestinal trunks.

The thoracic duct drained the lymph from the lower liThe thoracic duct drained the lymph from the lower limbs, pelvis, abdomen, left upper limb, left thorax, and mbs, pelvis, abdomen, left upper limb, left thorax, and left head and heck, that is the 3/4 parts of the body.left head and heck, that is the 3/4 parts of the body.

ⅡⅡ. The . The right lymphatic ductright lymphatic duct

It courses along the medial border of scaIt courses along the medial border of scalenus anterior at the root of the neck, ablenus anterior at the root of the neck, about 1 –5 cm long, and ends by opening iout 1 –5 cm long, and ends by opening into the right venous angle.nto the right venous angle.

It is the union of the right jugular trunk, rIt is the union of the right jugular trunk, right subclavian trunk, and right bronchoight subclavian trunk, and right bronchomediastinal trunk.mediastinal trunk.

The right lymphatic duct receives the lyThe right lymphatic duct receives the lymph from the right side of the head and mph from the right side of the head and neck through the right jugular trunk, froneck through the right jugular trunk, from the right upper limb through the right m the right upper limb through the right subclavian trunk, from the right side of tsubclavian trunk, from the right side of the thorax, right lung, right side of the hehe thorax, right lung, right side of the heart, and part of the convex surface of the art, and part of the convex surface of the liver through the right bronchomediastiliver through the right bronchomediastinal trunk. nal trunk.

Shortly, it receives the lymph from Shortly, it receives the lymph from the right and superior quarter of the the right and superior quarter of the body, while the lymph from the rest body, while the lymph from the rest greater part is collected into the greater part is collected into the thoracic duct, that is the 1/4 part of thoracic duct, that is the 1/4 part of the body.the body.

Section 3 The Lymphatic Section 3 The Lymphatic DrainageDrainage

Ⅰ Ⅰ. The lymphatic vessels and lymph nod. The lymphatic vessels and lymph nodes of head and neckes of head and neck

Ⅰ Ⅰ) The lymph nodes of head) The lymph nodes of head 1. Occipital lymph node1. Occipital lymph node 2. retroauricular lymph node2. retroauricular lymph node 3. parotid lymph node3. parotid lymph node 4. submandibular lymph node4. submandibular lymph node 5. submental lymph node5. submental lymph node

Ⅱ Ⅱ) The lymph nodes of neck) The lymph nodes of neck 1. Anterior cervical lymph node1. Anterior cervical lymph node (1) Superficial anterior cervical lymph node(1) Superficial anterior cervical lymph node (2) Deep anterior cervical lymph node(2) Deep anterior cervical lymph node ① ① Prelaryngeal lymph nodePrelaryngeal lymph node ② ② Thyroid lymph nodeThyroid lymph node ③ ③ Pretracheal lymph nodePretracheal lymph node ④ ④ Paratracheal lymph nodeParatracheal lymph node

2. Lateral cervical lymph node2. Lateral cervical lymph node (1) Superficial lateral cervical lymph node(1) Superficial lateral cervical lymph node (2) Deep lateral cervical lymph node(2) Deep lateral cervical lymph node ① ① Superior deep lateral lymph nodeSuperior deep lateral lymph node ② ② Inferior deep lateral lymph nodeInferior deep lateral lymph node Supraclavicular lymph nodeSupraclavicular lymph node Retropharyngeal lymph nodeRetropharyngeal lymph node

Ⅱ Ⅱ. The lymphatic vessels and lymph nodes of u. The lymphatic vessels and lymph nodes of upper limbpper limb

Ⅰ Ⅰ) Cubital lymph node) Cubital lymph node Ⅱ Ⅱ) Infraclavicular node) Infraclavicular node Ⅲ Ⅲ) Axillary lymph node) Axillary lymph node 1. Pectoral lymph node1. Pectoral lymph node 2. Lateral lymph node2. Lateral lymph node 3. Subscapular lymph node3. Subscapular lymph node 4. Central lymph node4. Central lymph node 5. Apical lymph node5. Apical lymph node

Ⅲ Ⅲ. The lymphatic vessels and lymph nodes of tho. The lymphatic vessels and lymph nodes of thoraxrax

Ⅰ Ⅰ) The lymph nodes thoracic wall) The lymph nodes thoracic wall 1. Parasternal lymph node1. Parasternal lymph node 2. Intercostal lymph node2. Intercostal lymph node 3. Superior phrenic lymph node3. Superior phrenic lymph node Ⅱ Ⅱ) The lymph nodes of the thoracic contents) The lymph nodes of the thoracic contents 1. Anterior mediastinal lymph node1. Anterior mediastinal lymph node 2. Posterior mediastinal lymph node2. Posterior mediastinal lymph node 3. Tracheobronchial lymph and pulmonary nodes3. Tracheobronchial lymph and pulmonary nodes

Ⅳ Ⅳ. The lymphatic vessels and lymph nod. The lymphatic vessels and lymph nodes lower limb es lower limb

Ⅰ Ⅰ) Popliteal lymph node) Popliteal lymph node Ⅱ Ⅱ) Inguinal lymph node) Inguinal lymph node 1. Superficial inguinal lymph node1. Superficial inguinal lymph node 2. Deep inguinal lymph node2. Deep inguinal lymph node

Ⅴ Ⅴ. The lymphatic vessels and lymph . The lymphatic vessels and lymph nodes of pelvisnodes of pelvis

Ⅰ Ⅰ) Internal iliac lymph node) Internal iliac lymph node

Ⅱ Ⅱ) Sacral lymph node) Sacral lymph node

Ⅲ Ⅲ) External iliac lymph node) External iliac lymph node

Ⅳ Ⅳ) Common iliac lymph node) Common iliac lymph node

Ⅵ Ⅵ. The lymphatic vessels and lymph . The lymphatic vessels and lymph nodes of abdomennodes of abdomen

Ⅰ Ⅰ) The lymph nodes of the abdominal ) The lymph nodes of the abdominal wallwall

Lumbar lymph nodeLumbar lymph node

Ⅱ Ⅱ) The lymph nodes of the abdominal ) The lymph nodes of the abdominal visceraviscera

1. The lymph nodes arranged along the celiac a1. The lymph nodes arranged along the celiac artery and its branchesrtery and its branches

Celiac lymph nodesCeliac lymph nodes ① ① Right and left gastric lymph nodesRight and left gastric lymph nodes ② ② Right and left gastroepiploic lymph nodesRight and left gastroepiploic lymph nodes ③ ③ Pyloric lymph nodesPyloric lymph nodes ④ ④ Hepatic lymph nodesHepatic lymph nodes ⑤ ⑤ Pancreaticosplenic lymph nodesPancreaticosplenic lymph nodes

2. The lymph nodes arranged along the s2. The lymph nodes arranged along the superior mesenteric artery and its branchuperior mesenteric artery and its brancheses

Superior mesenteric lymph nodesSuperior mesenteric lymph nodes ① ① Mesenteric lymph nodesMesenteric lymph nodes ② ② Ileocolic lymph nodesIleocolic lymph nodes ③ ③ Right colic lymph nodesRight colic lymph nodes ④ ④ Middle colic lymph nodesMiddle colic lymph nodes

3. The lymph nodes arranged along 3. The lymph nodes arranged along the inferior mesenteric artery and its the inferior mesenteric artery and its branchesbranches

Inferior mesenteric lymph nodesInferior mesenteric lymph nodes

① ① Left colic lymph nodesLeft colic lymph nodes

② ② Sigmoid lymph nodesSigmoid lymph nodes

③ ③ Superior rectal lymph nodesSuperior rectal lymph nodes

Section 4 The SpleenSection 4 The Spleen

In addition to the lymph nodes, several In addition to the lymph nodes, several organs are lymphoid in nature. These organs are lymphoid in nature. These include the spleen, the thymus gland, and include the spleen, the thymus gland, and the tonsils. They are named the lymphoid the tonsils. They are named the lymphoid organs. These organs, which have on organs. These organs, which have on direct association with the lymphatic direct association with the lymphatic system of vessels or with the lymph, are system of vessels or with the lymph, are an integral part of the body’s immune an integral part of the body’s immune system.system.

The The spleenspleen is the largest lymphoid organ.is the largest lymphoid organ.

1. Position1. Position

It lies principally in the left hypochondriac regiIt lies principally in the left hypochondriac region of the abdomen, between the fundus of the on of the abdomen, between the fundus of the stomach and the diaphragm, and its long axis istomach and the diaphragm, and its long axis is in line of the tenth rib.s in line of the tenth rib.

It is not palpable below the left costal arch unlIt is not palpable below the left costal arch unless it is enlarged or markedly dislocated. It is sess it is enlarged or markedly dislocated. It is soft, of friable consistence, and of dark purplish oft, of friable consistence, and of dark purplish colour. It is subject to injury from the blunt tracolour. It is subject to injury from the blunt trauma.uma.

2. Morphology2. Morphology

The spleen hasThe spleen has Two surfaces (diaphragmatic and visceral),Two surfaces (diaphragmatic and visceral), Two borders (superior and inferior),Two borders (superior and inferior), Two extremities (anterior and posterior).Two extremities (anterior and posterior). The diaphragmatic surface is convex, The diaphragmatic surface is convex,

smooth and faces upwards and smooth and faces upwards and backwards. It is in relation with the backwards. It is in relation with the abdominal surface of the diaphragm.abdominal surface of the diaphragm.

The visceral surface is directed towards The visceral surface is directed towards the abdominal cavity, and presents gastthe abdominal cavity, and presents gastric, renal, pancreatic and colic impressioric, renal, pancreatic and colic impressions. It has a long fissure near the center ons. It has a long fissure near the center of its visceral surface, termed the f its visceral surface, termed the hilumhilum, , which is for the entrance and exit of vesswhich is for the entrance and exit of vessels and nerves.els and nerves.

The superior border is sharper and is The superior border is sharper and is marked, near its lateral end, by one marked, near its lateral end, by one or two notches of variable depth, or two notches of variable depth, which can be recognized when the which can be recognized when the spleen is enlarged.spleen is enlarged.

The inferior border is blunter than The inferior border is blunter than the superior.the superior.

The spleen is almost entirely The spleen is almost entirely surrounded by peritoneum.surrounded by peritoneum.

Accessory spleenAccessory spleen: Frequently in the nei: Frequently in the neighbourhood of the spleen, small encapsghbourhood of the spleen, small encapsulated nodules of splenic tissue may be fulated nodules of splenic tissue may be found. They are known as the accessory sound. They are known as the accessory spleen, which has to be taken away in the pleen, which has to be taken away in the operation of splenectomy.operation of splenectomy.